Studies on the use of nano zinc oxide and modified silica in NR, CR ...

Chapter 1
Portland cement
20
The beneficial effects of ZnO additions to Portland cement have long
been known. They are retardation of setting and hardening (to reduce the rate
of heat evolution), improvement in whiteness and final strength.
1.4.2. Classification of fillers
Among the various compounding ingredients, fillers become one of
the most important components in the manufacture of rubber products, with
consumption second to rubber. Fillers are widely used to enhance the
performance of rubbers and other polymeric materials. In certain cases they
lower the cost of production of the final products. They influence almost all
properties, including density, hardness, tensile strength, impact strength,
chemical resistance, heat distortion temperature, processability and even the
appearance of the final products.
Filler may either be active or inactive according to the mutual
interaction between filler and polymer. This classification is rather arbitrary
since it is based on the difference in chemical composition and characteristics
of filler-particle surfaces, particle shape, size and treatment of surfaces by
coupling agents. The filler activity is controlled by the mutual adhesion of
the polymer and filler; it corresponds to the physicochemical character of the
polymer-filler interface, which determines the extent of sorption process on
the solid surface as well as the type of polymer-filler bonds. The results of
many studies describing the different aspects of filler-polymer interaction are
available in the literature. 37-38
Today there are hundreds of commercial fillers providing a
performance range from non-reinforcing to highly reinforcing; giving the
rubber compounder a wide choice of cost benefit option. Fillers used in
rubber compounds are generally classified into black and non-black fillers.